It is customary nowadays, both for stored-program control (SPC) and for motion control (MC), to model hierarchical running levels that are different in each case and are assigned software tasks for controlling the respective technical process. These tasks may perform system functions, but may also be user-programmed.
It is known from DE 197 40 550 A1 that process control functionalities of the stored-program controllers “SPC” and motion functionalities of MC controllers can be integrated in a uniform configurable control system.
This SPC/MC integration takes place in the form of interconnecting SPC and MC control modules. However, when the integration is carried out in such a way, an optimum and efficient task structure is not achieved for the entirety of the control tasks. Furthermore, with this type of integration it is mainly the classic MC functionalities, as are relevant in particular for machine tools, that are supported. Requirements for the controller, as they are known from the operation of production machines, are not optimally supported by this type of interconnection of SPC and MC control modules.
It is known from EP 0 735 445 A2 to use a separate waiting command (WAIT) for the operation of a machine tool or a robot. However, the waiting command (WAIT) described here still does not optimally support the control of production machines in particular.
In the application DE 19 93 19 33.2 it is proposed to use the clock of the communication system between the PC system and the peripheral devices for a change between a real-time operating program and a non-real-time operating program. Here, however, it is the task of this clock pickup from the communication system to allow the smoothest possible change to take place between real-time and non-real-time applications in an industrial process. In this configuration, the basic clock is only derived however from the clock of the communication medium and it is only used for the changing of the operating system mode of a PC system.
Furthermore, the methods customary nowadays for the programming of cyclical machines require different programs, the coordination of which is carried out by means of what are known as “event handlers”. The programming of cyclical machines is consequently laborious and an “event handler” adds to overhead and affects performance. Cyclical machines in the steady state are distinguished by a periodically recurring process or cycle. The productivity of the machine is directly dependent on this cycle. A shortening or reduction of the cycle enhances the productivity and the performance of the machine. Examples of cyclical machines are: packaging machines (for example tubular bag machines, filling machines or sealing machines) but also presses (for example roll-feed machines). For the performance of packaging machines, rapid printed mark synchronization and an associated rapid superposing of corrective movements are decisive, for example. Such objects are still not optimally achieved today.